In conventional wideband, high density magnetic signal processing, magnetic flux transferred to or from a magnetic storage medium permeates a magnetic core of a magnetic transducer (i.e., a head). During reproduction operation modes this flux produces an induced output voltage which, after suitable amplification, is a reproduced representation of the magnetic flux from the media that permeates the core and is suitable for use by a utilization device. During record operation modes, the permeating flux results from current applied to the transducer coil winding, and the flux fringes from a physical gap provided in the core for recording a representative signal in the magnetic storage medium.
One problem with prior art magnetic storage systems is that various losses occur during signal transfers between the magnetic storage medium and the transducer. One of the more significant losses, called "spacing loss", results from the physical spacing between the magnetic storage medium and the transducer. Spacing loss is particularly deleterious during reproduction operations where the effects of such loss are more significant. Prior efforts to reduce spacing loss primarily involved reducing the physical spacing by placing the transducer as close to the magnetic storage medium surface as operating conditions permitted. Such positioning, however, is accompanied by an increase in the likelihood of collisions between the transducer and magnetic storage medium, particularly in devices in which the transducer is normally supported above and out of contact with the storage medium surface, i.e., the transducer "flies" relative to the storage medium. On the other hand, if the transducer is in physical contact with the medium, damaging wear occurs due to the contact. However, it should be noted that if contact heads are used, the head is still separated from the storage medium by the carbon overcoat and lubricant that are standard in such disks.
U.S. Pat. No. 5,041,922 to Wood et al (hereinafter "Wood et al."), assigned to the assignee of the present invention, discloses a magnetic recording system which includes a magnetic medium having an overlying or underlying "keeper" layer of magnetically saturable high permeability material. The keeper layer facilitates denser storage media by reducing the fringing fields from the media. As disclosed in Wood et al., the properties of the keeper layer are selected to act as an extension of the head poles, thereby effectively bringing the head closer to the magnetic medium and reducing the spacing loss. Since one of the material properties of the head poles is high permeability, the keeper layer material in Wood et al was also selected to have high permeability.
U.S. Pat. No. 5,431,969 entitled "Method of Making a Magnetic Medium for Longitudinal Recording" to Michael L. Mallary (hereinafter "Mallary") discloses that a magnetic image layer (somewhat analogous to the keeper layer disclosed in Wood et al.) may have a uniaxial anisotropy. In particular, Mallary discloses several techniques for inducing the uniaxial anisotropy. However, each of the techniques is problematic in practice. For example, applying a magnetic field while the soft magnetic material of the image layer is being deposited interferes with the deposition process of the image layer when sputtering is used to deposit the layer. Specifically, the magnetic field which is used to establish the anisotropy in the magnetic image layer may interfere with the field which controls the sputtering process. The other techniques disclosed in Mallary to induce the anisotropy in the magnetic storage layer include (1) performing an anneal in a magnetic field, (2) controlling the angle of incidence in the case of vacuum deposition or (3) protexturing the substrate. However, these techniques are also problematic.
Hence, there is a need for a technique for inducing a desired anisotropy in the keeper layer to increase the system signal to noise ratio and reduce the intersymbol interference.